This invention relates to bullets generally, and in particular to small arms bullets in calibers from 0.224 inch to 0.500 inch of the bonded core, solid shank, soft nose, controlled expansion type used for hunting, self-defense, military, and law enforcement purposes.
This invention is an improvement on the bullets described in U.S. Pat. No. 5,621,186 dated Apr. 15, 1997, U.S. Pat. No. 5,641,937 dated Jun. 24, 1997, and U.S. Pat. No. 4,879,953 dated Nov. 14, 1989.
Present day bullets are assembled with a cartridge filled with a powder charge. When fired, the bullet travels through a gun barrel having spiral grooves with spiral lands between the grooves. The diameter of the bullet is equal to or slightly less than the diameter of the grooves but greater than the diameter of the lands so that spiral grooves are formed in the cylindrical section of the bullet that follow the spiral and cause the bullet to be rotating on its longitudinal axis when it leaves the barrel. This improves the accuracy of the gun.
Thus, the pressure exerted on the bullet by the burning powder of the cartridge accelerates the bullet as it travels through the barrel and also provides the force required for the lands to cut spiral grooves in the bullet causing it to be spinning on its longitudinal axis as it leaves the barrel.
It is an object and feature of this invention to reduce the force required to cut the spiral grooves and thereby increase the muzzle velocity of the bullet, which also increases the kinetic energy of the bullet without reducing the rate at which the bullet spins.
It is a further object of this invention to provide a controlled expansion bullet that will obtain higher muzzle velocities with the same pounds per square inch pressures provided by the cartridge that are established by the American National Standards Institute and published by Sporting Arms and Ammunition Manufacturers, Inc. These standards are generally known in the ammunition industry as xe2x80x9cANSI/SAMMI.xe2x80x9d
It is also an object of this invention to substantially reduce the length of the portion of the outer surface of the bullet that is in engagement with the lands and grooves of the barrel as the bullet travels through the barrel and thus increases the amount of the energy produced by the burning powder that is available to accelerate the bullet as it travels through the barrel.
The twist of the grooves in the barrel of a firearm produces the spin of the bullet and the twist ranges from one turn in 9.5 inches to as slow as one turn in 20 inches. The number of rifling lands in a conventional barrel normally ranges from as low as four to as high as six. The height of the rifling lands ranges from 0.0025 inch to 0.007 inch.
It is a further object and feature of this invention to provide a bullet having a circumferential groove in the base shank section of the bullet having a diameter less than the diameter of the lands between the grooves to decrease the force required to force the bullet through the barrel and thereby increase the muzzle velocity of the bullet.
Another object of this invention is to provide a uniform and equal friction reduction on all weights of bullets of the same diameter.
These and other objects, advantages, and features of this invention will be obvious to those skilled in the art from a consideration of this specification including the attached drawing and appended claims.